The present invention relates to an thin-film electroluminescent display panel and, more particularly, to a thin-film electroluminescent display panel shielded by two glass substrates and a protective liquid disposed therebetween.
A conventional thin-film electroluminescent (EL) display panel sealed by two glass substrates and a protective liquid is disclosed in Kawaguchi et al, U.S. Pat. No. 4,213,074 issued July 15, 1980, assigned the common assignee and entitled "THIN-FILM ELECTROLUMINESCENT DISPLAY PANEL SEALED BY GLASS SUBSTRATES AND THE FABRICATION METHOD THEREOF". The disclosure of this patent is incorporated herein by reference.
In the structure of the thin-film EL display panel, it is very important and necessary to completely seal this display panel and, in addition, to prevent any moisture from penetrating into the housing of the display panel defined by the pair of glass substrates. The presence of the moisture mainly lowers the intensity of the EL light from the EL display panel because to the damage of picture elements.
In this respect, the above patented structure of the EL display panel inherently has a defect in that it is rather difficult to make a complete seal including an injection hole for passing a protective liquid therethrough such that the injection hole remains highly resistant to temperature change. Another defect is that moisture from the atmosphere may penetrate into the damaged seal of the injection hole. Moisture can penetrate into a cavity defined by two glass substrates through the damaged seal of the injection hole much easier than through the combined portion between the glass substrates. The cross-sectional size of the injection hole is much greater than that of the beforementioned combined portion of the substrates.
Therefore, it is highly desirable to provide complete seal including the injection hole so as to completely prevent any moisture from the surrounding environment from entering into the inner cavity.